Tube formation and products formed thereby

ABSTRACT

A method of forming thin walled ductile tubes by wetting the inside of a thick walled tube with a liquid and passing the tube between rollers to flatten the tube and simultaneously elongating the tube and reducing the wall thickness thereof, and then applying pressure to the inside of the tube to restore a tubular shape, the tube being preformed into a radiator core or the like prior to the application of pressure and stretched to avoid wrinkling.

United States Patent 1191 11] 3,763,681 Flintoft Oct. 9, 1973 TUBE FORMATION AND PRODUCTS 2,850,793 9/1958 Schweller et al. 29/157.3 v FORMED THEREBY 1,951,394 3/1934 Chase et al. 29/157.3 V [76] Inventor: William A. Flintoft, 59 Branson FOREIGN PATENTS OR APPLICATIONS Clearvlew, Australia 714,380 7/1965 Canada 72/367 [22] Filed: May 22, 1972 Primary Examiner-Richard J. Herbst [21] Appl 255405 Attorney-Vern L. Oldham et al.

[30] Foreign Application Priority Data [57] ABSTRACT May 25, 1971 Australia 4993/71 I Oct. 7, 1971 Australia 6554/71 A method 8 waned ductlle tubes by ting the inside of a thick walled tube with a liquid and [52] Cl 72/57, 29/1573 V, 113/118 D Y passing the tube between rollers to flatten the tube 51 1111.01 B2ld 53/02 and Simultaneously elongating the tube and reducing 58 Field of Search 29/1573 R, 157.3 v, the Wall thickness there, and then applying Press"re 2 9/202 D; 1 13/1 C; 72/57, 58, 60 61 t0 the inside of the tube to restore a tubular shape, the tube being preformed into a radiator core or the like [56] References Cited prior to the application of pressure and stretched to UNITED STATES PATENTS avmd wnnklmg 2,845,695 8/1958 Grenell 29/ 157.3 V 7 Claims, 8 Drawing Figures PATENIEU 9W5 3.763.681

sum 10F 4 PATENTED BET 975 SHEET u [1F 4 This invention relates to improvements in and relating to a method and means for tube formation and to products manufactured thereby such as heat exchangers, radiators and the like where it is desirable to utilize tubes which are bent to special configurations to give the necessary heat exchange and where also it isnecessary in some cases to provide fins or increase the surface area of the heat exchanging members.

BACKGROUND OF INVENTION It is customary in the production of tubes to draw tubes to a required size such as by passing them successively through a series of dies which either by pressure extrusion or by tension applied to the tubes achieve the desired configuration and reduction of wall thickness depending on the number of passes of original stock from which the tube is made through the dies.

There are however problems in producing tubes of relatively thin wall section by the known methods and there are also problems in forming these tubes into required configurations such as where flattened tubes are required or where such tubes, particularly flattened tubes, must be bent to provide a particular formation such as in radiator cores or the like.

It is known that thin wall tubes can be produced from thicker walled stock by flattening the tubes and applying sufficient pressure to reduce the wall thickness of the tubes, and to then reform the tubes to the required configuration by the application of internal pressure, such as shown in co-pending United States Ser. No. 228,208. One of the main problems in providing bent flattened tubing is to bend such tubing and to then open the flattened member without causing wrinkling and uneven areas at the bend of the finished product.

lt is therefore the object of this invention to provide an improved method of and means for producing thin walled tubing and to form the tubing into required configurations.

This invention also relates to the construction of a heat exchanger or other devices using shaped tubular construction.

Heat exchangers as currently used take many forms. For example, heat exchangers which are used on motor vehicles are formed from a series of noncircular seamed thin tubes or brazed thin metal strips of such configuration that both the water passing through the water conduits formed by the bracing and the air passing between them is subject to considerable turbulence so as to obtain a high efficiency. However, such heat exchangers are of relatively high cost and have a short life when compared with the heat exchangers of this invention and one of the objects of this invention is to provide a means whereby a heat exchanger can retain a high degree of efficiency but be of lower cost and longer life.

Heat exchangers which are utilized in many refrigerators, air conditioners and other thermodynamic heat pumps are frequently formed from round tubing or extruded aluminium tubing having internal ribs (and sometimes external ribs) to support tubing as it is bent around small radii, the extruded aluminium tubing having heat transfer strips bonded to it by a process which does not give a very high heat transfer efficiency. Such units contain more metal than is necessary under this invention, are expensive to form and have an efficiency lower than that which can be obtained by'means of this invention.

SUMMARY OF INVENTION According to this invention a tube of any required dimensions is fed through rollers or the like to flatten a tube, a number of passes of the tube through the rollers or the like being effected according to the amount of thinning of the walls which is required, but according to the present method, before such tubes are formed, the hollow stock is treated by injecting a liquid such as soluble oil into the stock, the purpose of which is to provide a layer on the inside of the stock which has then been found to prevent pressure welding of the tubes as they are being formed.

Once the internal surface has been so treated, the stock can be passed through the rollers with the application of sufficient pressure to reduce the stock to ribbon form having a wall thickness required for the final product, and there will be no problems due to fusion because of the pressure used.

' Having thus formed a tubular ribbon of the required dimensions and wall thickness, bending of the ribbon to shape is effected and the ribbon is then placed into a die and then has pressure applied to the inside of the flattened tubular ribbon to expand the tube in the die to give it the required configuration, but before such application of the pressure for expansion, the tube has a stretching force applied to it so that as the tube is expanded to fit the die, it is also stretched at least at the bend localities.

We have found that this stretching action avoids wrinkling of the tube at bend localities and provides a much more uniform cinfiguration of the final product.

To apply the pressure to the tube, the flattened tubular stock extends through both ends of the die, and in one end a pair of clamping jaws clamp over the flattened tubular stock to prevent any expansion thereof while at the other end a second pair of clamping, jaws clamp over the flattened tubular stock but have half round openings extending along the clamping faces of each so that when the clamping jaws are together the two half-round openings together form portion of a circular opening through the clamping jaws, the circular opening having the central portion of the projecting end of the flattened tubular stock extending through it. In the embodiment shown the first mentioned jaws can be portions of the die. A lance is used to open the tube and is in the form of a spade or knife-like member having a sharpened point, and increasing in thickness away from the sharpened point or edge, the spade or knifelike member then merging into a conical case on one end of a tubular portion. An opening extends from the tubular portions through the spade portion and through a side wall of the spade portion to allow passage of liquid at pressure from within the tubular portion of the lance into the space within the flattened tubular stock.

A hydraulic cylinder is provided with a guided piston rod, and the guided piston rod, and the guided piston rod has the tubular portion of the lance secured thereto, the cylinder then functioning as the lance guide means although additional guide means can be utilized if desired.

An oil pump is connected through valve means to both the lance and to the hydraulic cylinder.

After forming the tube in this way it can then be finned or otherwise treated where it is to be used as a heat exchanger but the methods of fitting or the like such as by the application of thin material between parallel parts of the tube structure and then dipping to solder the fins to the outside of the tubes can take any usual form and does not necessarily form any part of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates diagrammatically how a tube which is to be flattened and have its walls reduced in thickness is first treated by injecting a material such as soluble oil to avoid pressure welding of the walls during the reducing and elongating step.

FIG. 2 shows the tube after having its inside walls wetted, being rolled to produce a flattened thin walled tube.

FIG. 3 is a plan of such a tube prebent to approximately the shape of the tube when used in a radiator core or the like.

FIG. 4 is a purely diagrammatic plan showing the preformed tube inserted in a die in which it is subsequently expanded by pressure.

FIG. 5 is a fragmentary view of the die assembly because it will be noted that in FIG. 4, one member of the die is movable in relation to the other to stretch the die before pressure is applied, and in FIG. 5 is shown the position of the tube after stretching with the tube pulled hard around the bend of the inner die.

FIG. 6 is a view corresponding to FIG. 4 but with the dies in the position where the tube has been stretched and has had the pressure applied to blow it out to fill the cavity in the die, in which position the tube is restored with a cavity with the required configuration and size in readiness for building into a radiator or the like such as by applying fins or other heat exchanging devices between the parallel sections of the shaped tube. 40case FIG. 7 is a somewhat diagrammatic view of the machine, showing mainly the fixed die and the movable die and the ejectors by means of which the finished tube is removed from the die, the die in this case being shown as composed and including adjustable members so that differing widths of finished tubing in its shaped form can be produced.

FIG. 8 is an enlarged plan of the machine showing particularly the form of die used in which a tube is stretched and expanded.

DESCRIPTION OF PREFERRED EMBODIMENT The tube 1 which can be produced of ductile material in any convenient manner, has a liquid such as soluble oil introduced into it from a nozzle 2 or other means or could be dipped as a coil or the like into a bath, the purpose being to line the inner walls of the bore 3 of the tube with a material such as an oil or the like which will prevent adhesion of the surfaces when the tube is rolled under heavy pressure to produce elongation of the tube and thinning of the walls.

The tube 1 is shown being elongated and thinned in FIG. 2 where it passes between rollers 4 and 5, the number of passes to reach the required thinning and elongation of course depending on the final dimensions required of the flattened tube in relation to the starting dimensions of the tube.

Annealing between passes through the rollers can of course be effected.

It is found that when a tube is passed between rollers in the manner outlined, the tube is compressed to flattened shape and is elongated as the wall thickness is reduced, there being some tendency to slightly widen the strip but this is generally not great as the rolling action has the effect of extending the metal in the direction of the rolling and in this way very thin walled tubes can be produced and in fact the method forms a cheap and effective way of obtaining such tubes.

When such a tube is to be formed into a shape such as for use in a radiator core or the like, the tube is bent as shown in FIG. 3. The tube being then placed into a two part die as illustrated in FIG. 4 the die comprising what we will term an outer member 6 and an inner member 7, the members forming between them stretching means for the tube 1 in that the outer member of the die has a number of recesses 8 in it which form between them fingers 9, the inner die member having recesses 10 in it which fonn between them the fingers l l.

The preshaping of the tube is such that when it is placed into the die as shown in FIG. 4, the bends 12 of the tube fit neatly around the ends of the fingers 9 and 11 but when relative movement is caused to take place between the outer die member 6 and the inner die member 7, the tube is stretched within the cavity of the die and when stretching is completed, which is the position shown in FIG. 6, the bends 12 of the tube are pulled tightly around the ends of the fingers 9 and 11 as shown particularly in FIG. 5.

After this stretching liquid is injected into the tube from the end 14 while the other end 15 of the tube is sealed by clamping it, and the liquid then expands the tube into the die as shown in FIG. 6 to form the final tubular structure.

Referring now to FIGS. 7 and 8, in which a machine is shown for carrying out the invention, the die member 6 is carried on a base 20 so that it is movable, the die member comprising a series of fingers as previously explained which are interleaved as it were with the fingers 9 of the fixed member 7. The base 20 is connected by a link 22 to a ram of a hydraulic cylinder 23 rigidly attached to the frame 24 of the machine.

The space in which a tube is being formed by stretching and blowing is designated 25.

Rods 26 which are carried on a member 27 mounted on the ram 28 of a hydraulic mechanism 29, are for ejection of the expanded product.

Stretching of the tubes is effected by relative movement between the members 6 and 7.

The actual machine shown in FIG. 7 and 8 is a universal machine, which is not essential for the purposes of the invention, but which allows selection of the number of bends and the length of the joining portions so that radiator cores or other tubular products which are being manufactured can be varied in their size, and this will be best appreciated from FIG. 8 where a tube 1 is shown inserted in the machine having fingers 9 as earlier described which are of a substantial length and which are connected together so that they can be advanced forwardly when pressure is applied to the hydraulic cylinder 23, the ends of these fingers 9 engaging the bends of the tubes as shown while the ends of the fixed fingers ll engage the bends at the opposite end of the tube structure.

To allow variation in size of the tubular structure being formed, a series of bend forming blocks can be positioned along the inner die fixed member 7, that is the blocks 30 can be positioned between the fingers 11 and locked in any required position on the member 7, while at the other end, a bar 32 is locked in position on the outer moving die member 6 and carries the bend-forming portions 33 which are positioned between the fingers 9.

In this way the bend-forming blocks 30 and the bendforming portions 33 can be moved towards or away from each other to accommodate any particular size of tubular structure which is to be formed.

Similarly as the structure is built up of a series of fingers 9 and 11, these can be removed in part to leave a width of structure required for a particular radiator core or the like and thus the device allows selection of both the length and the width of tubular structures formed by the machine.

The injector which engages the end 14 of the tube comprises a main operating cylinder 35 which can urge forwardly a lance-carrying member 36, the lance 37 of which can be engaged in the end of the tube to provide a communication of pressure fluid to the inside of the tube, this end of the tube being clamped between one jaw of a clamp 38 fitted to the fixed member 7 of the machine while the other jaw moves with the member 6 which is urged forward by the cylinder 23 so that the tube is firmly clamped around the nozzle through which the pressure fluid discharges after the tube has been stretched, the final closing of the clamp 38 taking place under influence of cams which engage the clamps 38 and 44 on a moving head 40 which is mounted on the ram 41 of the hydraulic cylinder 42 and is guided on pillars 43 attached to the main frame 24, the purpose of the member 40 being to move down onto the dies 6 and 7 and assist in firmly holding the fingers 9 and 1 l in correct position during the pressurising of the tube the downward movement of the head 40 causing cams, only the cam 39 being shown, to engage the two clamps 38 and 44.

The sliding members 45 and guide the clamps 38 and 44 respectively and control the pressures under influence of the cams on the head 40 but it will be realised that any required clamp operating mechanisms can be provided.

A block 48 having blades 49 on it is secured to the head 40 above the area where the tube is being expanded, the blades 49 engaging between the fingers 9 and the fingers 11 to act as top spacers to avoid distortion of the fingers when expanding pressure is applied to the tube.

From the foregoing it will be realised that a simple and effective device is provided by means of which thin walled tubes can be formed in a highly effective manner without any risk of welding together of the tubes due to pressure and also such flattened tubes can then be shaped as required to form radiator cores or any other structures, the forming of the tubes being a simple matter due to their flattened section prior to bending, the stretching ensuring that the expansion of the tubes by pressure then expands the metal into the dies without wrinkles or corrugations to form tubes of uniform cross section even at the bends and thus allow high efficiency of flow to be attained in such structures.

I claim:

1. Improvements in a method of tube formation wherein thin walled ductile tubes are formed by the steps of a. wetting the inside of a thick walled tube with a liquid such as a soluble oil,

b. passing the tube between rollers in a longitudinal direction of the tube a number of times while maintaining sufficient pressure on the rollers to flatten the tube and simultaneously elongating the tube and reducing the wall thickness thereof during each pass,

c. annealing the tube between passes,

d. bending the flattened tube about a generally transverse axis before placing it into a hollow die having a cavity greater than the thickness of the flattened tube but to limit expansion of the tube,

e. stretching the tube in the said die to force the inside of the bent portions against the die, and

f. then expanding the tube into the die by applying pressure to the inside of the said tube, whereby significant wrinkling of the bent portions is avoided.

2. Improvements in the tube formation method according to claim ll including the steps of bending the flattened tube about a generally transverse axis at a number of spaced localities to form substantially parallel sections joined by bends, and the said tube is placed into a cavity, formed in a two-part die having fingers defining the cavity, the ends of the said fingers at least nearly engaging the insides of said bends, one part of the die being movable relatively toward the other whereby when said one die part is moved the flattened tube is stretched to give firm engagement of the fingers with the inside of the said bends, such relative movement of said one die part leaving a cavity into which the tube can be expanded when the pressure is applied within the tube.

3. Improvements in tube formation wherein thin walled ductile tubes are formed by passing the tube lengthwise between rollers to flatten and elongate the tube by reducing the wall thickness, then bending the flattened tube about generally transverse axes to form a heat exchanger core, placing the so formed tube into a die having a cavity greater than the thickness of the flattened tube but to limit expansion of the tube, applying a stretching force to the said tube while in said die to force the inside of the bends so formed against the die, then expanding the inside of the said tube by applying fluid pressure within the said tube to force the walls of the said tube to conform to the said die, whereby significant wrinkling of the bends is avoided.

4. Improvements in tube formation according to claim 3 wherein the flattened tube is bent about a generally transverse axis at a number of spaced localities to form substantially parallel sections joined by bends, and the said tube is placed into a cavity formed in a two-part die having fingers defining the cavity, the ends of the said fingers at least nearly engaging the insides of said bends, whereby when one part of the die is moved relatively toward the other, the flattened tube is stretched to give firm engagement of the fingers with the inside of the said bends but leave a cavity into which the tube can be expanded when the pressure is applied within the tube.

5. A machine for use in tube formation wherein preflattened tube which is bent about a generally transverse axis to comprise a series of parallel sections joined by bends, placing the so formed tube into a die having a cavity greater than the thickness of the flattened tube but to limit expansion of the tube, which machine comprises a pair of dies forming between them a cavity to receive the said flat shaped tube, means to move one die relative to the other to stretch the said tube by engagement of die members with the inside of the bends, and means to expand the said tube comprising clamp means to seal one end of the tube, and pressure applying means to engage the other end of the tube and apply pressure thereinto to expand the said tube into said die.

6. A machine according to claim wherein the dies each comprise fingers forming between them recesses, the fingers of one die filling into the recesses within the other die to define around the fingers the cavity into which the tube is to be expanded, said fingers being movable longitudinally in said recesses whereby the bent tube can be stretched when one part of the die is moved relatively toward the other die, said stretch causing firm engagement of the ends of the fingers with the inside of the said bends of the tube so that when pressure is applied within the tube the flattened tube will be expanded into a hollow tube in the cavity without significant wrinkling.

7. A machine according to claim 5 in which each die comprises fingers forming between their recesses, said fingers being formed by replaceable plates secured to a support, the inner ends of said plates being adapted to engage the inside of bends of the said flattened tube, bend forming blocks between the said plates of one die to form adjustable ends of that die, bend forming portions between the plates of the other said die to form adjustable ends of that die, and means on the said dies to clamp shut one end of the said flattened tube and to clamp said other end to a fluid supplying nozzle whereby said flattened tube is expanded.

i t 0 t 

1. Improvements in a method of tube formation wherein thin walled ductile tubes are formed by the steps of a. wetting the inside of a thick walled tube with a liquid such as a soluble oil, b. passing the tube between rollers in a longitudinal direction of the tube a number of times while maintaining sufficient pressure on the rollers to flatten the tube and simultaneously elongating the tube and reducing the wall thickness thereof during each pass, c. annealing the tube between passes, d. bending the flattened tube about a generally transverse axis before placing it into a hollow die having a cavity greater than the thickness of the flattened tube but to limit expansion of the tube, e. stretching the tube in the said die to force the inside of the bent portions against the die, and f. then expanding the tube into the die by applying pressure to the inside of the said tube, whereby significant wrinkling of the bent portions is avoided.
 2. Improvements in the tube formation method according to claim 1 including the steps of bending the flattened tube about a generally transverse axis at a number of spaced localities to form substantially parallel sections joined by bends, and the said tube is placed into a cavity, formed in a two-part die having fingers defining the cavity, the ends of the said fingers at least nearly engaging the insides of said bends, one part of the die being movable relatively toward the other whereby when said one die part is moved the flattened tube is stretched to give firm engagement of the fingers with the inside of the said bends, such relative movement of said one die part leaving a cavity into which the tube can be expanded when the pressure is applied within the tube.
 3. Improvements in tube formation wherein thin walled ductile tubes are formed by passing the tube lengthwise between rollers to flatten and elongate the tube by reducing the wall thickness, then bending the flattened tube about generally transverse axes to form a heat exchanger core, placing the so formed tube into a die having a cavity greater than the thickness of the flattened tube but to limit expansion of the tube, applying a stretching force to the said tube while in said die to force the inside of the bends so formed against the die, then expanding the inside of the said tube by applying fluid pressure within the said tube to force the walls of the said tube to conform to the said die, whereby significant wrinkling of the bends is avoided.
 4. Improvements in tube formation according to claim 3 wherein the flattened tube is Bent about a generally transverse axis at a number of spaced localities to form substantially parallel sections joined by bends, and the said tube is placed into a cavity formed in a two-part die having fingers defining the cavity, the ends of the said fingers at least nearly engaging the insides of said bends, whereby when one part of the die is moved relatively toward the other, the flattened tube is stretched to give firm engagement of the fingers with the inside of the said bends but leave a cavity into which the tube can be expanded when the pressure is applied within the tube.
 5. A machine for use in tube formation wherein pre-flattened tube which is bent about a generally transverse axis to comprise a series of parallel sections joined by bends, placing the so formed tube into a die having a cavity greater than the thickness of the flattened tube but to limit expansion of the tube, which machine comprises a pair of dies forming between them a cavity to receive the said flat shaped tube, means to move one die relative to the other to stretch the said tube by engagement of die members with the inside of the bends, and means to expand the said tube comprising clamp means to seal one end of the tube, and pressure applying means to engage the other end of the tube and apply pressure thereinto to expand the said tube into said die.
 6. A machine according to claim 5 wherein the dies each comprise fingers forming between them recesses, the fingers of one die filling into the recesses within the other die to define around the fingers the cavity into which the tube is to be expanded, said fingers being movable longitudinally in said recesses whereby the bent tube can be stretched when one part of the die is moved relatively toward the other die, said stretch causing firm engagement of the ends of the fingers with the inside of the said bends of the tube so that when pressure is applied within the tube the flattened tube will be expanded into a hollow tube in the cavity without significant wrinkling.
 7. A machine according to claim 5 in which each die comprises fingers forming between their recesses, said fingers being formed by replaceable plates secured to a support, the inner ends of said plates being adapted to engage the inside of bends of the said flattened tube, bend forming blocks between the said plates of one die to form adjustable ends of that die, bend forming portions between the plates of the other said die to form adjustable ends of that die, and means on the said dies to clamp shut one end of the said flattened tube and to clamp said other end to a fluid supplying nozzle whereby said flattened tube is expanded. 